1. Field of the Invention
The present invention relates, in general, to a valve stem sealing device used for preventing oil from entering a combustion chamber through a gap formed between a valve guide and a valve stem and, more particularly, to a valve stem sealing device with an oil seal being capable of rotation with the valve stem, thereby preventing the oil seal from being abraded and the oil from entering the combustion chamber.
2. Description of the Prior Art
As well known to those skilled in the art, an intake valve is mounted to an internal combustion engine, thus allowing a mixed fuel to flow into a combustion chamber. Also, the engine has an exhaust valve for exhausting combustion gas into the atmosphere.
FIG. 2 shows the construction of one typical valve, which may be an intake or an exhaust valve for internal combustion engines. It is important to note that the two valves are the same construction.
As shown in FIG. 2, a port 3 of a combustion chamber is opened or closed by the reciprocating motion of the valve which is driven by the rotating motion of a cam 2. The valve stem 12 of the valve 10 vertically reciprocates under the guide of a valve guide 7 of a cylinder head.
The cylinder head, with the cam 2, also has a valve control mechanism. In order to effectively operate both the cam 2 and the valve control mechanism, cooling and lubrication oil is supplied into the cylinder head.
However, the lubrication oil may be unexpectedly introduced into the combustion chamber through a gap formed between the valve guide 7 and the valve stem 12, thus reducing the combustion efficiency of the engine. Furthermore, such an unexpected introduction of oil into the combustion chamber may cause the engine to break down. Thus, it is preferable to mount an oil seal 20 onto the top of the valve guide 7 in an effort to prevent such an introduction of oil into the combustion chamber.
The oil seal 20 is fitted over the valve stem 12, with a support means 22 surrounding the seal 20 so as to hold the seal 20 in its place. The support means 22 is preferably made of a steel plate having a certain thickness. The support means 22 is fixed onto the top of the valve guide 7. The oil seal 20 has an annular blade 20a, which inwardly extends from the inner surface of the seal 20 and comes into close and movable contact with the side wall of the valve stem 12.
Thus, the oil seal 20 removes any gap from the junction between the valve guide 7 and the valve stem 12. That is, the valve stem 12 vertically reciprocates the inside of the oil seal 20, with the annular blade 20a being brought into close contact with the side wall of the valve stem 12, thereby preventing the oil from entering the combustion chamber.
When the valve 10 is reciprocally moved, the valve 10 is somewhat rotated. Also, in the operation of the valve, the valve head 14 comes into repeated contact with the port 3 at a high speed. As a result, the combustion chamber is repeatedly opened or closed by the reciprocating and rotating motion of the valve head 14.
However, in such a valve stem sealing device structure according to the prior art, the annular blade 20a of the oil seal 20 is quickly abraded due to the rotating motion of the valve 10, with the oil seal 20 being fixed to the top the valve guide 7 by the support means 22. Therefore, the typical sealing device may fail to prevent oil from flowing into the combustion chamber. In such a case, the sealing device reduces the combustion efficiency of an engine and, cause the engine to break down.